A dominant feature of modern surgical procedures is to minimize the size of the region within the patient affected by the surgery. Such "minimally invasive" surgery has led to major growth in surgical procedures performed through various types of endoscopes. Previously, surgery was dominated by open surgical procedures in which the surgeon opens the region of the patient requiring attention, and carries out the procedure directed by his or her direct viewing of the surgical field. Recent advances in optics, laser surgery, electrosurgery, as well as miniaturized manipulation techniques have opened up a radically new approach and added significantly to the range of procedures the surgeon can call upon in treating the patient. More and more, the surgeon will place a few small incisions into the patient, and insert therein various viewing and surgical devices. Typically in such procedures, the surgical field will be illuminated and viewed by means of optical fiber devices inserted into the patient. The surgery is then performed by means of miniature devices also inserted through such small incisions, while the surgeon observes and guides the interaction of tissue and instruments on a television monitor.
Such endoscopic surgical procedures are becoming standard in general surgery, gynecology, thoracic surgery, orthopedic surgery, pulmonary medicine, gastroenterology, and are developing rapidly in neurosurgery, spinal surgery and other areas. This trend towards endoscopic surgery has been especially dominant in abdominal surgery, in which the abdominal cavity provides ample opportunity for surgery through an endoscope (typically referred to as a "laparoscope" when used in the abdominal cavity, and the procedures performed through the laparoscope are referred to as "laparoscopy".). Among the procedures commonly performed by abdominal laparoscopy are gall bladder removal, hernia repair, appendectomy, bowel resection, hysterectomy, removal of ectopic pregnancies, and others.
However, laparoscopic abdominal surgery is hindered by the confined space within the abdominal cavity in which to manipulate tissues and instruments. In conventional, open surgery, the various organs can typically be moved about to provide better viewing of the surgical field and better access for the surgeon. This is not convenient in laparoscopic surgery and alternative ways to operate in confined body cavities must be developed.
The preferred technique at the present time is to inflate the abdominal cavity with a suitable gas, maintaining a positive gas pressure to inflate the abdominal cavity in a manner not too dissimilar to a balloon. Such pneumoperitoneum provides additional working area for the surgeon, allowing instruments to be manipulated in the abdominal cavity with less obstruction. The thrust of the present invention is to describe an improved instrument for insufflation of the abdominal cavity for the purpose of maintaining pneumoperitoneum during laparoscopy.
Conventional insufflation suffers from several disadvantages. Perhaps the most serious disadvantage is the relatively low flow rates of gas: typically of the order of 6-15 liters per min. (1/m). As more incisions are used in laparoscopy, leakage becomes a more serious problem and the maintenance of pneumoperitoneum becomes difficult or impossible. This is exacerbated in certain gynecological procedures in which a direct escape path for gas through the patients vagina becomes available. A particular problem is created when laser or electrosurgery create significant amounts of smoke during the procedure. High suction rates are required to remove such smoke from the patient. The typical insufflator is unable to compensate and the patient's abdomen deflates.
Increasing the flow rates of insufflation gas would help in the maintenance of pneumoperitoneum, but increases the dangers to the patient of over pressurization. It is an important object of the present invention to provide high-flow rate insufflation (typically 10-40 1/m) with over pressurization safety measures.
Another problem with conventional insufflation is the quality of the insufflation gas delivered to the patient. Carbon dioxide is the typical insufflation gas. But carbon dioxide reacts with the abdominal fluids to create small amounts of carbonic acid, increasing postoperative discomfort for the patient. Also, the delivery of cold, dry insufflation gas to the patient tends to desiccate the serosa of intra-abdominal cavity structures, increasing the possiblity of intra-abdominal adhesions. The apparatus of the present invention addresses these particular problems with conventional insufflation as well as providing for high flow rate insufflation in a safe manner.